1. Field of the Invention
The present invention pertains to the art of washing machines and, more particularly, to a pump cycling system for controlling a drainage operation in a washing machine.
2. Discussion of the Prior Art
During operation, a clothes washing machine proceeds through a series of wash and rinse cycles. At least a terminal portion of each rinse cycle includes a spin cycle portion wherein a clothes article containing tub or basket is spun at a relatively high speed in order to extract water from the clothes. During the spin cycle, a drain pump is typically run full time in order to remove water from the washer. For a substantial portion of the spin cycle, the rate at which water is removed from the clothes is much lower than the rate that the pump can function. This results in the pump working in a mixture of air and water. Such operating conditions can cause premature wear on the pump, as well as developing excessive noise.
To address these concerns, various systems have been proposed which function to limit the operating time of a washing machine drain pump. For instance, it has been proposed in the art to activate the drain pump for only a prescribed percentage of the spin cycle, during intermittent, predetermined periods throughout the cycle, for a timed duration which can vary with wash load, or simply based on a sensed water level within the machine. Although these systems aid in addressing the problems noted above, excessive pump operation times still exist in accordance with these prior art arrangements, particularly in connection with the timed pump operation based systems. Based on at least these reasons, there is a need in the art for a control system which will effectively and efficiently reduce the cycle time of a drain pump in a washing machine.
The present invention is directed to a system and method for effectively controlling the time a drain pump of a washing machine is activated during a drain operation conducted as part of a spin cycle. In accordance with the invention, at least one dynamic operating parameter of the washing machine is sensed and used to control the activation and deactivation of the drain pump in a cyclic manner.
In accordance with the most preferred form of the invention, activation of the drain pump is dependent upon extraction speed and time. More particularly, the spin speed of the washing machine tub is monitored and when this speed has dwelled at a specified speed for a predetermined amount of time, a controller is employed to automatically cycle the drain pump for a prescribed time period. In accordance with a second embodiment of the invention, the torque employed to drive the washing tub during a spin cycle is monitored to trigger a drain operation. That is, a sensed increase of torque to the washing tub is indicative of the presence of an excess of water. As the torque decreases, the pump is cycled off. These control arrangements can actually be employed individually or in combination in accordance with the invention. Furthermore, input from a water level sensor could be used in connection with an additional, redundant system, i.e., as a verification measure for use in combination with one or more of the dynamic based pump cycle time control systems of the invention.
Based on the above, it should be apparent that the system of the present invention relies upon one or more specific dynamic variables of the washing machine in order to accurately and effectively control the operation of the drain pump so as to minimize cycle times. In any event, additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views.